Electromagnetic stirrer



Aug. l0, 1965 K. FoLGER ETAL ELECTROMAGNETIC STIRRER Filed March 19,1963 INVENTORS K fm; F

United States Patent O 3,200,185 ELEQTRGMAGNETEC STIRRER Kre Folger andGsta Karlsson, Vasteras, Sweden, assignors to Alirnanna SvenskaElelitrisira Aktiebolaget, Vasteras, Sweden, a Swedish corporation FiledMar. 19, 1963, Ser. No. 266,247 Claims priority, application Sweden,Mar. 21, 1962, 3,130/62 v 3 Ciairns. (El. 13-26) The present inventionrefers to an electromagnetic stirrer for metallurgical containers, suchas furnaces consisting of stirrer winding, iron core and teeth ofmagnetic material extending from said core.

Stirrers of this type are previously known, for example through the U.S.Patent 2,960,556. In this is shown a stirrer winding with straight corelegs and with teeth brought out towards the furnace bottom, which teethare embedded in a ceramic protective layer protecting the stirrerwinding from falling charge. Perpendicular to the teeth are fixed coversover the stirrer coil of non-magnetic material.

The present invention relates to an improvement of this construction andis characterised in that the teeth extending towards an air gap at thefurnace bottom or side at least partly are situated between the coils ofthe Winding and are provided with a centre part extending to the airgap. Such a construction achieves, inter alia, the advantage in relationto earlier kno-wn constructions that the erect-ion is easier at the sametime as the manufacture is cheaper. With a proposed embodiment theWinding is made coil-wound and the teeth are made in three parts, twoinsulating side bars, which in height do not extend essentially outsidethe coils and an uninsulated centre portion, extending from the spacebetween two coils to the air gap. A similar construction means smalllosses and at the same time small dimensions.

These and other embodiments and details of the invention are moreclearly illustrated in accompanying figures, of which FIGURE 1 shows afurnace bottom with applied electromagnetic stirrer. FIGURE 2 shows astirrer winding with the cover removed. FIGURE 4 shows partly in sectiona stirrer winding and FIGURE 3 shows a section along line A-A in FIGURE4.

In FIGURE 1 is shown schematically a furnace bottom 11 for a furnace inwhich an existing charge may be stirred by means of a multi-phase lowfrequency electromagnetic stirrer 12, in principle made according to theU.S. Patents 2,513,082 and 2,960,556. The teeth of magnetic material andincluding parts 20 and 21 are brought forward to a narrow air gapbetween the stirrer 12 and the furnace bottom or side. The stirrer ismade with straight core legs, which means a simplification of the iinalform and an easier erection. The stirrer according to FIGURE 1 is madewithout cover, but such a cover suitably of ceramic material may ofcourse from a protection point of View be proposed (see also FIGURE 4).

In FIGURE 2 is shown the stirrer in FIGURE 1 seen from the furnacebottom. The coil-wound stirrer windings 14 are fastened by band-formedcoil cover 15 of magnetic material, which cover extends substantiallyperpendicular to the coils. The teeth extending towards a charge air gapclose to the furnace bottom 11 or side lie partly between the coils.

In FIGURES 3 and'4 is shown a detailed embodiment of an electromagnetic,coil-wound, multi-phase and low frequency stirrer for steel charge.Between the coil ends 16, which are bent down and possibly cast intoconcrete or the like or non-conducting and non-magnetic com- 32'0,Patented Aug. 1i), 1965 pound, the winding 17 extends in a plane alongthe stirrer. Under the winding a straight laminated iron core 18 isplaced and perpendicular to the windings 17 are placed band-formed slotcaps 15, suitably of magnetic material. These caps are held fast byinsulated fastening bolts 19 between the windings 17 and through slotsengaged in the iron core 1S, along the whole length of the core,wherebythe bolts existing in the slot are not subjected to damagingmagnetic field.

Between the coils 17 and between slot cap plane and iron core areinserted outer parts 2li of the teeth, insulated (for example enamelled)and made in magnetic material. Between these is inserted an uninsulatedcentre portion 21 of teeth, whole or spliced, of magnetic material. TheWidth of this part is considerably greater than for each of the parts 20and is chosen so that magnetic saturation will not occur in this. Itextends to the air gap at the furnace bottom. Above the stirrer isplaced a ceramic cover or layer 22, partly embedding the parts 21 of theteeth and intended to protect the stirrer against falling charge. Theinsulation of the side bars 20 may of course also occur by means ofwinding, loose insulating layers, etc. The coil ends 16 are castsuitably into non-magnetic compound, such as concrete or cement (seeIndustriall Teknilr, profylax, No. 5/ 1963). In the different conduitsin the coils are included cooling medium channels 23 and the coolingmedium, for example water, which circulates through the differentconduits in normal manner, for example via the tube conduits 24.

The two side bars 20 should suitably extend along the whole or thegreater part of the stirrer, while the centre portion 21 with theprominent tooth parts are divided into parts, lying between thedifferent slot caps 15 and their fastening bolts 19 respectively.Between the two outer bars 20 a space thus arises for these fasteningbolts 19 close to the slot cap 15.

The invention may also be applied for coil-winding and for other thanstraight core legs. It may be varied in many ways within the scope ofthe following claims.

We claim:

1. Electromagnetic stirrer for metallurgical containers, comprising astirrer winding comprising coils for electric current having spacesbetween them, and an iron core on the side of the coils remote from thecontainer, teeth of magnetic material having parts extending from pointswithin said spaces kbetween said coils substantially below a planethrough those parts of the coils positioned nearest the container topoints outside such spaces and substantially closer to the containerthen such plane, and spaced from said container to provide an air gap.

2. Electromagnetic stirrer in accordance with claim 1, in which saidteeth each comprises a central portion extending along the whole lengthof the teeth and of less width than the spaces, and two insulated sidebars extending within the spaces on each side of the central portion andpositioned adjacent the coil sides.

3. Electromagnetic stirrer in accordance with claim 1, in which theteeth and the coils extend sidewards in one direction along thecontainer bottom; strip formed caps of magnetic material extendingperpendicular to such direction, and bolts clamping said caps to saidcoils and parts of the teeth.

References Cited by the Examiner UNITED STATES PATENTS RICHARD M. WOOD,Primary Examiner.

1. ELECTROMAGNETIC STIRRER FOR METALLURGICAL CONTAINERS, COMPRISING ASTIRRER WINDING COMPRISING COILS FOR ELECTRIC CURRENT HAVING SPACEDBETWEEN THEM, AND AN IRON CORE ON THE SIDE OF THE COILS REMOTE FROM THECONTAINER, TEETH OF MAGNETIC MATERIAL HAVING PARTS EXTENDING FROM POINTSWITHIN SAID SPACES BETWEEN SAID COILS SUBSTANTIALLY BELOW A PLANETHROUGH THOSE PARTS OF THE COILS POSITIONED NEAREST THE CONTAINER TOPOINTS OUTSIDE SUCH SPACES AND SUBSTANTIALLY CLOSER TO THE CONTAINERTHEN SUCH PLANE, AND SPACED FROM SAID CONTAINER TO PROVIDE AN AIR GAP.